lemmonhead

so those of us who tinker and tune the ourselfes. What kind of load curve do you have. Do you stick with the stock BDEL curve. Personally I dont do the taper at the high RPM I make it flat.
load offeset = 100
BDEL
169 -(from low RPM-3500)
155 - (4000-8,000 RPM)

so instead of a sideways bell shape curve, I get a peak and just a small taper and stays pretty flat.
I usually hit 270 2byte load peak, then taper to 240 and stays around there until redline.

RazorLab

iTrader: (8)

If you are running the stock turbo and run a 255 load in the BDEL + BCLO then you are using error correction to add boost up top.

It is very doubtfull that you are holding an actual 255 load up top with the stock turbo. Maybe up until about 6000-6500 rpm, but after that it, the actual load will drop to about 230 or so at 7k, in 3rd gear. This data I am grabbing from a Evo 9 running 100 oct and holding 23psi at 7k.

The issue with this is that you will also be running more boost in the higher gears as you are not using the BDEL tables the way they should be, to add or subtract boost to try and always maintain target load. The car will add more boost in higher gears to try and hit 255 load, which it will never do with the stock turbo. This means you are probably getting max upward correction.

I personally would advise to get your BDEL + BCLO closer to your actual desired load.

Also, max number in the BDEL table is 159.4 so you aren't running 169.

If you do need higher target load, let's say 262, then use 200 in your BCLO and 62 in your BDEL for that RPM.

so the BDEL would look something like this:

62.5
62.5
62.5
62.5
62.5
62.5
62.5
62.5
62.5
60
58
58
56
50
43
35

lemmonhead

yes correct 159 not 169 sorry about that. and yes buy 7000 rpm it wont hit your desired load, but the point i was making is not to max it out on top and not purposely taper it.

RazorLab

iTrader: (8)

Using the correct target load isn't tapering it. The load curve will always "taper" down even if you had a straight 23psi across. Why not just use WGDC to give yourself the correct boost and then target load to keep it all tidy? That is what it is designed to do.

How you have it currently, it will add more boost in higher gears, the problem with this is that it won't be as consistent.

TouringBubble

iTrader: (2)

I was going to post earlier, but I thought it would be best to add images ...



That makes for these results ...

RazorLab

iTrader: (8)

TouringBubble, that is using psi-target boost so target load doesn't apply.

Also looks like you need to either up the target-psi at 7k or bring down your 100 wgdc there.

Getting some downward correction.

TouringBubble

iTrader: (2)

It is psi based boost control, but I thought I'd share anyway. I know it's not 100% ... it varies with temp though. I specifically designed the settings (WGDC and TBEC) to work with varying temperatures. It's a must here ... it was like 80* yesterday while I was working in the yard and it's currently 53* with a suspected frost tonight.

If you remember, I have been talking about defining a basic WGDC curve and letting TBEC take over for consistent boost. This is the result.

lemmonhead

ya nice, see you dont need any taper, my point I was trying to make is why does everyone think you need to taper, if you are capable of holding it flat do it!!!

merkzu

iTrader: (4)

The BDEL curve only determines error correction though. You don't want to tune your boost by forcing the error correction to kick in. The WGDC curve determines your boost - you want the BDEL to follow the load curve created by the WGDC so that your error is as close to 0 as possible

So if you want to reduce taper, set your WGDC to 100 in the high rpms, but set the BDEL to what the load actually is.

RazorLab

iTrader: (8)

What merkzu said.

TouringBubble

iTrader: (2)

Here is a question ... why is it bad to let the TBEC define the boost? I see absolutely no problem with it.

and, Lemmon, you need taper for thermal management. I make more power with 24 psi in the mid range and 20.5 psi up top than I do with 26 psi in the mid range and the max of 22.5 psi up top. You could get similar results with moderate boost over the entire rev range, but I like having a wider power band and more torque down low.

lemmonhead

very good point, "thermal managment"
but I see guys with upgraded intercoolers, less restriction piping ect to lower the temps and upgraded actuators or external wastegates. hell even meth kits but people still make boost taper so much, 26psi peak to 20 redline. I would think they dont need so much taper for thermal managment. Unless maybe they are after more timing up top than boost?

roger smith

iTrader: (4)

It seems to me a lot of people run manual boost controllers. The taper is all that can be done using those. But I'm sure you know.

Oh wait but your post asks for designed load curve huh? So that must assume people using ecu-controlled boost?

Anyway I agree with TouringBubble. It depends on your desired power output. Big boost down low tapering down as RPM rises makes for nice down-low torque like a rally car.

TouringBubble

iTrader: (2)

Well, what you don't want, no matter how much meth you shove in or how thick your IC is, is to run the turbo at it's maximum speed for an extended length of time. Once the turbine hits that maximum velocity it does nothing but heat the air. Once you get to that point your potential power will begin to fall off.

I've run 26 psi in the mid range and 22 psi up top on 93 with honestly no ill effects. I didn't even lose that much power up top. I tapered it down a little because that also didn't lose much power. I could add an extra 2º or so up top and make just a tad more power with less boost. For me the choice was simple ... lower boost means slower turbine speed and extended life.

I say do the testing yourself just like I did. I ran 3 different scenarios back to back (with some cooling allowed between). 26 psi and max boost up top, 24.5 psi with taper to 20 psi and 22 psi with just a hint of taper to 21 psi. The 24.5 tapered boost profile made more power over pretty much the entire rev band.

merkzu

iTrader: (4)

I just wouldnt do it that way because the TBEC alters the entire boost curve up or down. So if you have BDEL set 10% higher than what you are really hitting, TBEC raises the WGDC curve 10% to try and hit it. It doesnt matter at RPMs where the WGDC cells are 100, but when you upshift you may hit WGDC cells that are not 100, and they will get the 10% increase too so you will overboost.. then it will try to correct down. It might not hurt anything depending on the setup but it's not good if you are trying to keep a stable boost curve.

I made a lot more power holding out as much boost as possible up top but E85 might be making a difference there.